A. Field of the Invention
The present invention relates to door and window hardware. More particularly, the present invention relates to a mechanically stable and ergonomically improved door and window sash lock.
B. Description of the Prior Art
Sliding windows or patio doors in a building are made for letting in necessary light and air into the room while allowing occupants to have a comfortable viewing of the surrounding nature. At the same time, such doors or windows should be able to lock out harmful elements and potential intruders.
Window latches and locks that are also applied to doors have been developed as the windows in the modernized buildings have long been evolved all together. Of different types of slider window, a single-hung type window is structured to have an upper outside pane in a stationary sash and an inside pane in a sliding sash guided in a window frame along its vertical path between a raised level positioned over the upper sash to half open the window and a lowered position to close the window opening in cooperation with the upper sash. A double-hung type window has two vertically sliding sashes movable in parallel planar paths in a single frame. There are also horizontal sliders. A gliding window has two sashes with at least one sliding horizontally past the other. The respective sashes of the double-hung windows may be made to swing inwardly for the purpose of a safe cleaning but they must be returned to their vertical abutting positions when the window is to be locked. Normally, in the closed position, the mating sashes have the respective proximal sides overlapped to offer the necessary sealing. Therefore, most latches are conveniently positioned near the meeting areas of the two sashes at the exposed surface of the inner sash while the mating keeper or strike is fixed to the accompanying outer sash.
Known latches for windows have their inherent drawbacks. Automatic window sash locks as depicted in U.S. design Pat. No. 395,222 to Fountaine comprise a main latch body attached to a slide-open sash for automatically engaging a fixed keeper on the companion sash or the sash itself that incorporates in its profile a notch so that the sashes are immobilized in the frame when the window is closed. Such sash locks generally include a user-operated component handle to release the automatic locking mechanism, which only needed the sliding closure of the sash to push in a bolt of the sash lock before it protrudes back into engagement with the keeper or notch. To streamline the one-handed user operation in lift or sideway slide opening of the window, the release handle or lever of the sash locks is adapted to be depressed by index to little fingers while the thumb presses on the underside of the proximal sash part to release the lock and slide the sash in one action.
However, the lever needs a substantial projection from the main latch body taking up space upward as well as toward the user for the bolt to create a proper lever or bolt action inside the latch device. This makes a bulky and unappealing lock structure that sticks into the viewing area of glass panes. Under the superficial problem lies a mechanical disadvantage to have to apply a large circular force to retract a locking bolt out of engagement with the counterpart of the other sash. For the internal actuator to move the bolt easily, the lever must extend above and beyond the latch device itself as long as possible. However, such deflecting lever movements produce a long-term adverse force against the secure joint between the latch device and sash during their combined lifetime because normally there is only a couple of fasteners to endure the releasing depressions at repeated window openings.
Hence, there is need for a small form factor sash lock that is not only visually unobtrusive but also mechanically stable and ergonomically fit.